"Tipuna is one of my favorites. Great bedding! In other places nearby, if I recall, this same unit displayed the big cross-beds, so it's precurser is dune sand, but it has been altered (I believe). It needs to be placed in context to the upper unit, chemically speaking."

Tipuna caught my attention when I first saw it, but work took me away from the pc. Yes, it definitely has the same properties we've seen in the big cross-beds and YES, it does seem to have been altered, but how?

"The thin joint coating at the lower right has not been discussed, either."

I know, I'm sure they noticed it too!

"It is at high angle to the bedding, is probably re-cemented, and may have be evidence for a ground-water conduit to feed the Sabkhaesque evaporative surface above. One of the wicks, if you will."

Yes! Cemented is a much better descriptive word than "frozen" as I used above. Cemented by those sulfur rich acidic liquids. But, how can you have clean cracks like that from a dehydrated (bare with me here) surface and then have the edges go through another wet/dry cementation process? This area must have had periods of hydrothermal, "ground water conduit" activity which may also explain those suspended (also cemented) spikes or as you called them, wicks.

"As for frost, check out this arm-waving."

I saw that.

This makes sense to me:

"If it is jarosite, then we need a source of Sulfur, as there are not iron sulfides in the meteor. Here's my arm-wave: a small amount of occasional morning frost combined with sulfate dust (blowing in the wind) combine to create a small amount of sulfuric acid, which feeds off the kamacite/taenite (Fe-Ni) to create a small amount of jarosite as a weathering product. Just a thought."

Repeated layering/deposition of frost and thirsty, porous Sulfur dust settling in the pits (protected by the Martian winds), may very well do that. I hope someone does a lab recreation.

I love this stuff.